The Burrowing Owl

Kaeti Barrett

John Tuxill

Fair 206A[pic 1]

March 9th, 2018

Animal Profile                               

        The Burrowing owl (Athene cunicularia) is part of the Strigidae family. “Other names include (Tecolote Ilanero) in Spanish and (Chevêche des terriers) which is French” (All about Birds, 2017). I’ve always had an interest in owls because we hear them sometimes off and on where we live. I’d wonder what kind of owl it was because I only thought there were a few types of owls, and how wrong I was about that when I did my research: 171 species known, to be exact. To do this project I talked to my cousin who loves owls and has written papers on different owls. I also looked up online, in books, and read up on everything I could find out about these birds and found out a lot more than I expected about their life history.

           I started off wondering how did they get their name, and do they have a nickname? For instance the Arctic owl is formally called the Snowy owl. Yes, the Burrowing owl’s nick name is the howdy bird. They got the nickname from when they bobbed their heads, and the cowboys took that as a friendly greeting. Out of the vast amount of 171 different owls that exist, they are the only bird/owl that lives underground in “burrows,” hence the name Burrowing owl, however seabirds also nest in burrows too. My next question was much more in depth; what makes Burrowing owls different from other owls? Well, Burrowing owls are diurnal, (awake during the day) and do more hunting in the daytime whereas other owls do their hunting at night. They also have better color vision than any other owl out there. Another fact is most male owls are bigger than female owls, but that is not the case for the Burrowing owl; they’re the same size. Another question I had was, are they endangered? While there are still a lot of Burrowing owls today, “populations declined by about 33% between 1966 and 2015," according to the North American Breeding Bird Survey, in February 2017. The survey also said, “it has notably gone down in Florida, North and South Dakota and on the coast of California.” They also estimated in 2016, "a global breeding population of 2 million, with 31% spending some part of the year in the U.S., and 15% in Mexico.” The species rates a 12 out of 20 on the Continental Concern Score and is not on the 2016 State Of the Birds Watch List. The species is listed as Endangered in Canada and as a species with Special Protection in Mexico." Some of the reasons the numbers have been declining are because of pesticides, shooting, and getting tangled or caught in fences or other human-made hazards, as well as being hunted by Great horned owls, badgers, foxes, cats, and dogs. At the same time in All About Birds/Burrowing Owls according to Ray Poulin, Danielle Todd, et al, in 2011, ”Burrowing owls have benefited from protective legislation, reintroduction and habitat protection programs, and artificial nest burrows. Because they do not require large uninterrupted stretches of habitat, these owls can benefit from the protection of relatively small patches of suitable land."  I also wondered what would happen if the climate continued to change under global warming conditions. Apparently, droughts could pose a problem for Burrowing owls through reduced nesting success and greater fire frequency due to heat rising with higher rates.

               In Sibley’s 2014 guide when you see their appearance, they have bright eyes. “They are small with long legs, but short tails. They have a round head and do not have ear tufts. They’re about the same size as an American robin, but much bulkier and a tiny bit smaller than a Western screech owl." Both sexes measure to be about the length of 7.5- 9.5 in and weigh 5.3 oz. If you see one, you’ll notice that the adults are brown birds mottled with sandy-pale spots on the upperparts. The breast is spotted, grading to dark brown bars on the belly. They have a bold white throat and eyebrows, and yellow eyes. The brown juveniles are less mottled than adults, with buffy-yellow underparts and wing patches. While Burrowing owls are capable of producing a variety of cooing, warbling, rasping, clucking, screaming, and rattling sounds, the species is not primarily vocal unless you’re near their burrow. Most commonly heard is a quail-like two-note cooing made by males during mating and territorial defense. Young owls utter eepcalls and rasping sounds, the most intense and prolonged of which may scare away predators by mimicking a rattlesnake's warning

              One behavior of Burrowing owls is that they usually stay close to the ground as they fly, hover, walk, or run, seizing prey in their talons. Between forays for food, they sleep on dirt mounds at their burrow entrances or on depressions in the ground. Disturbed owls bob jerkily up and down, as do hunting owls pinpointing prey. “Males defend their territories against other males by vocalizing, displaying in a weaving crouch with feathers fluffed, or chasing and attacking with outstretched talons.” (J.R. Sauer, 2011)

            Burrowing owls are sit-and-wait predators, and they will not move until the prey is in range. These owls are known to catch insects during flight. However, they are often seen to chase down much of their prey on foot. They have a flexible diet that encompasses both small vertebrates and large invertebrates. Burrowing owls primarily eat insects, tiny rodents, amphibians, small lizards, toads, and frogs. These owls are even capable of ingesting relatively large prey such as Eared doves. They are known to prey on crickets, termites, katydids, spiders, wolf spiders, scorpions, and ground beetles. Burrowing owls also feed on fruits and seeds, especially prickly pear and cholla cacti.

            Many scientists have done experiments examining Burrowing owls, and their diets around the Northwestern states and have come up with interesting results. The first study was in the Columbia basin of south-central Washington and north-central Oregon during 1977-78 and 1980-81. In Gregory A Green’s article in 1993 on pg. 89 he said,

        “Vertebrates mainly rodents, comprised only 9.6 percent of the total prey numbers                 contained out of the 6,328 pellets but 87.3 percent of the biomass in the two samples                 combined. In Washington the prey usage was twice as the amount was in Oregon;                 Washington being 17.1 percent and Oregon being at 8.4. What contributed to the                 difference was habitat, soil type and rainfall on the owl's prey.”

They collected and analyzed a total of 6,328 pellets of which 769 were obtained from 5 nests.

            In another study done by David Hall, they examined diets of Western burrowing owls. They tested them based on contents of pellets (undigested food that’s regurgitated) and abundant prey remains collected year-round at burrows. In each of the regions the most common prey items, based on percent frequency of occurrence, were crickets and grasshoppers, beetles, rodents, sun spiders, and scorpions.

            “The most common vertebrate prey we found was kangaroo rats  (Dipodomys spp.).                 True bugs (Hemiptera), scorpions, and western harvest mice  (Reithrodontomys                         megalotis) occurred most frequently in pellets from the Great Basin Desert region.                 Kangaroo rats (Dipodomys spp.) and pocket mice (Perognathinae) were the most                 important vertebrate prey items in the Transition and Mojave Desert regions,                         respectively. Their Frequency of occurrence of any invertebrate prey was high (>80%) in         samples year-round but dropped in winter samples, with scorpions and sun spiders                 exhibiting the steepest declines. The frequency of occurrence of any vertebrate prey                 peaked in spring samples, was  intermediate for winter and summer samples, and was                 lowest in fall samples” (Gregery B., David Hall et al. 1993, pg 90).

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